A correspondent of Nature writes that, in roaming over the hills and rocks in the neighborhood of Kendal, near Lancaster, England, which are composed chiefly of limestone, he had often found what are called “musical stones.” They are generally thin, flat, weather-beaten stones, of different sizes and peculiar shapes, which, when struck with a piece of iron or another stone, produce a musical tone, instead of the dull, heavy, leaden sound of an ordinary stone. The sound of these stones is, in general, very much alike, but sets of eight stones have been collected which produce, when struck, a distinct octave.

— Frank H. Stauffer, The Queer, the Quaint and the Quizzical, 1882

See also The Musical Stones of Skiddaw.